For the purposes of recording properties of defined points in a measurement environment, in particular data with a spatial reference, a multiplicity of measurement methods have been known since antiquity. Here, the position and alignment of a surveying device and direction, distance and angle to measurement points are recorded as spatial standard data. The theodolite or a total station constitutes a well-known example of such surveying devices or geodetic devices. Such devices have an angle measurement function and rangefinding function for determining direction and distance to a selected target. In the process, the angle and distance variables are established in the internal reference system of the device. For the purposes of determining the absolute position, these variables still need to be linked with an external, absolute reference system, for the purposes of which the precise absolute deployment of the surveying device, as the position and orientation of the internal reference system thereof in the external reference system, generally serves as a basis.
In order to precisely establish the absolute, i.e. geo-referenced, deployment of the surveying device, the position and orientation thereof can be calculated precisely, as indirect geo-referencing, from geodetic measurements in the current deployment in relation to absolutely referenced target points. Geodetic measurements are direction and distance measurements by means of the angle measurement and rangefinding functions of the surveying device and the target points are punctiform stationary and calibrated points, e.g. church tower tips or objects specifically installed for geodetic surveying, e.g. target markers on a building site, which are present in the measurement environment of the surveying device. The position and orientation are calculated from the measured location relative to the internal reference system of at least three target points and the known absolute location thereof. In other words, the transformation between the two reference systems is determined from the location of the target points in the internal reference system of the surveying device and in the external reference system. A disadvantage of such a method is that the required geodetic measurements to a plurality of target points distributed in the environment are time-consuming and cost intensive.
According to the prior art, labor-intensive and time-consuming methods are required for determining the current deployment, even for measurements that recur in the same measurement environment and are connected with a disassembly and a new setup or displacement of the assembled surveying device. By way of example, if setting out and centering is undertaken without much time outlay for setting up the surveying device exactly above a previous deployment, there is an offset in such situations between the previous, first deployment, i.e. the position and orientation at the earlier location, and the current, second deployment, i.e. the current position and orientation of the surveying device. Such recurring measurements in the same measurement environment from similar locations and with, in the process, a different deployment occur, for example, on building sites for surveying object points newly built since the last survey or a plurality of measurements occur with an offset of the surveying device so as to be able to completely register extended environmental objects, e.g. surveying all four sides of a house or registering object positions, e.g. a street, which are covered, for example by a building or a rocky ledge, as seen from one location.
Direct geo-referencing as an alternative method for determining the current deployment by means of a GNSS receiver connected thereto supplies less precise results and moreover it is disadvantageous in that the method is bound to the reception of GNSS signals, which may be inhibited, e.g. in tunnels or densely built-up areas.